This invention relates to metal-encased objects, especially ceramic and metal objects. This invention further relates to the method for preparing such metal-encased objects.
Because of their high resistance to heat and oxidation, ceramic materials are used to manufacture a wide variety of industrial parts. Often, it is necessary or desirable to encase the ceramic part in metal so that it may be welded to other metal parts. For example, the catalytic converters used in automobiles comprise a ceramic honeycomb structure, coated with catalyst, which structure is then encased in a metal can so that it may be welded to the automobile chassis. The process presently used for encasing the catalytic converters in metal is costly and labor intensive. A piece of metal cut in a clam-shell shape is bent around the previously coated and fired ceramic substrate, held in that position and welded closed. Even if the metal casing is tightly fit around the converter at room temperature, the metal will expand differentially from the ceramic at higher temperatures, causing the ceramic to metal fit to loosen, allowing the converter to move within the casing during use and become damaged.
There is, therefore, a clear need for metal encased articles which can be prepared by a less costly and labor intensive method than that currently used and which will not possess the above-mentioned disadvantages arising from the differential expansion of the ceramic and the metal.